The present invention generally relates to circular and flat knitting machines capable of manufacturing apparel, including hosiery and like articles. More particularly, the invention relates to a method and apparatus for transferring a loop or loop from a selected needle to an adjacent needle by enlarging the loop on the selected needle and then inserting the other needle through the enlarged loop before the selected needle releases the loop. The term loop is used below to define the segment of yarn being manipulated by the needles, but the term "stitch" can be used interchangeably. This application also discloses an apparatus and method whereby a no-run and conventional stitch pattern can be changed during machine operation by altering the position of a cam, or by having two cams in operation at the same time. By the term "no-run" is meant a stitch with an interlocking feature that prevents a hole from enlarging along a length knitted fabric, and is synonymous with the terms run-proof and run-less. This type of stitch provides knitted products, particularly stocking or pantyhose products, extra life. As disclosed herein, a no-run stitch is also used in combination with a conventional stitch to provide additional patterning possibilities.
This application also discloses a needle specifically designed to facilitate loop transfer in the apparatus and method described below.
Circular knitting machines knit together multiple strands of yarn into a tubular fabric, hosiery blank or other structure. The hosiery blank is then finished according to conventional processes to create finished hosiery articles, such as socks, hose and stockings. Such machines include a plurality of needles positioned in axial slots formed in an exterior surface of a rotatable needle cylinder. Each needle includes a shank having opposed ends. A hook is formed in a top end of the needle shank and a butt is formed in the bottom end of the needle shank. A plurality of sinkers are mounted in a sinker ring positioned on a top end of the needle cylinder such that the sinkers are alternately positioned between the needles. Circular knitting machines also include a feeder mechanism that delivers yarn onto the passing needles. The yarn forms a loop or loop around each needle.
Flat bed knitting machines carry out similar functions on a flat bed, forming a flat fabric which can then be formed into drapes, garments or many other products.
Hosiery articles with decorative patterns formed by open-work in the fabric created by transferred knitting loops is old and conventional. The space not occupied by the transferred loop creates a hole in the fabric, and the pattern of holes in the fabric collectively create the desired decorative effect. Heretofore such designs have been limited to relatively coarse gauge fabrics due to the difficulty in transferring very small loops between fine gauge needles. Thus, there is a need for a knitting machine and method which permits the creation of decorative open-work patterns in fine gauge knitted fabric, including fine gauge fashion hosiery, such as tights, pantyhose and similar articles, particularly with the capability to create no-run stitches.
For example, U.S. Pat. No. 3,838,583 to Rumi et al. discloses apparatus which modifies a circular knitting machine so that it can create openings with transfer loops. The Rumi apparatus includes a dial plate eccentrically positioned over and internal to a needle cylinder and a planetary gear eccentrically positioned over and external to the needle cylinder. The upper surface of the dial plate is provided with a plurality of internal punches slidable in a radial direction, and the upper surface of the planetary gear is provided with a plurality of external punches slidable in a radial direction. The internal punches are inclined suitably in the direction opposite of the direction of rotation. Devices are provided to control the axial movement of the internal and external punches and cam means are provided to raise the needles to the level of the punches. Finally, a plurality of movable sinkers are positioned on the needle cylinder and each partially surround one of the needles. The strands of yarn loop around the needles and extend over the sinkers.
In operation, the selectors raise a specified needle or group of needles past their normal working position. The loop on the needle catches on a needle shoulder which raises the loop above the sinker surrounding the needle. The sinker, which has an end hook, then advances and its hook enters the loop causing the loop to enlarge. Immediately afterwards, either of the two punches enter the loop by passing adjacent to an undercut in the needle. The needle is then returned to its normal position leaving the loop on the punch. The punch transports the loop to the intended needle which is raised up through the loop. That needle continues to rise until the loop is removed from the punch and then returns to its normal position. If the internal punch is used, the loop is transferred to the needle preceding the needle from which the loop was taken. If the external punch is used, the loop is transferred to the needle following the needle from which the loop was taken.
The Rumi apparatus, like other existing apparatus used for transferring loops, first removes the loop from the selected needle and then transfers that loop to the following needle. This practice can only be used effectively on coarse gauge knitting machines. Having the distance from one needle to another of 2.35 mm or greater prevents the apparatus from reliably transferring the loop because of the small size of the needles and loops on knitting machines operating with distances between needles of less than 2.35 mm, or 120 needles in a cylinder diameter of 31/2 inches. A missed transfer creates a defect which results in a less than first-quality product. The missed transfer problem is naturally exacerbated when the diameter of the needle cylinder is decreased and/or the number of needles being operated is increased.
Consequently, transfer loops cannot be reliably made on prior art fine gauge circular knitting machines. A need, therefore, exists for a method and apparatus for effectively transferring loops from a selected needle to an adjacent needle without dropping a loop and without creating other defects in hosiery articles manufactured on a circular knitting machine capable of creating fine gauge articles.